Spider-hunting Wasps

All ants, bees and wasps belong to the suborder Apocrita in the order Hymenoptera. The 'spider-hunting wasps' are all classified under the family Pompilidae which contains six genera named for the southern African region. Each family contains several or numerous, variable or similar-looking species. The females are generally larger than the males. The largest species - up to 50mm in length, dwarf the smallest species at less than 10mm. Each is adapted to hunting spiders, which also vary greatly in size in every conceivable habitat. One common characteristic of all the spider-hunting wasps is that they immobilise their prey with a paralysing sting (normally the female wasp). They then drag (large prey) or carry the spider to a crevice, pre-dug hole or nest chamber, where an egg is deposited on the living but immobile corpse before the spider is covered or sealed in.

The wasp egg hatches at around 10 days and the larva feeds on the spider until it is fully developed, at which stage it spins a dense cocoon around itself. The larva will then lie dormant for months until temperature and humidity stimulate pupation. After a pupal period of around three weeks, the adult emerges to continue the cycle. Some of the large spider-hunting wasps make a loud 'rattle' with their wings in flight and this has been supposed to assist hunting by causing movement in the prey. This is not substantiated by the fact that they spend a lot of time searching the ground in apparent silence.

SPIDERS (ORDER ARANEAE)

Many thousands of species of spiders occur in all habitats and in almost every conceivable shape and size around the globe. They travel around the world in human cargoes and the smallest species are capable of intercontinental travel on threads of silk carried by the winds.

In our region, the most familiar species are the larger orb web spinners - (Genera - Nephila and Argiope) - and the big, ground dwelling rain spiders (Palystes) and baboon spiders. Often called tarantulas, there are eight genera of baboon spiders in the family Theraphosidae - the largest of which is the golden-brown baboon spider - Pterinochilus sp.

Similar to the wasps mentioned above, the female spiders are generally much bigger than the males and in some cases hundreds of times bigger. With the orb-web spinners the female constructs the main web and is large enough to secure sizeable prey. The diminutive males fertilise the females but frequently become prey to the voracious females.

With the baboon spiders (that can live for over 20 years) the females dig and maintain breeding holes in the ground around which they hunt for prey. The males are nomadic in search of females and food and make temporary shelters.I have highlighted here only some large species of these two groups. For further information I would direct readers to the two spider books by Martin R Filmer and Astri and John Leroy and to the insects books by Dr John Ledger / Bannister and Picker, Griffiths and Weaving.